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Saturday, March 1, 2008

Myth of cockroach’s immunity to nuclearirradiation busted

Cockroaches survived much more than humans

Fruit flies, flour beetles tougher than cockroaches

Last year, the Myth Buster TV team from the Discovery Channelannounced that they would find out experimentally whethercockroaches would be the only livingform to survive a nuclear war (The Hindu, November, 1, 2007). OnJanuary 30, this year (Episode number 97), the team busted themyth which was in their priority list from day one.

The announcement that the myth buster team will conduct anexperiment received wide media coverage; surprisingly, the mediavirtually ignored the results of the experiment.

The experiment

The staff of the Pacific Northwest National Laboratory at Hanfordsite (U.S.) assisted the team to expose three groups of Germancockroaches (50 each) to 1,000, 10,000 and 100,000 radsof gamma radiation using an irradiator located in the basement of abuilding at Hanford. The fourth group of 50 cockroaches served ascontrol... (Rad is a unit of radiation dose; a dose of 450 rads may kill50 per cent of the persons exposed) They exposed similar groups of50 flour beetles and 100 fruit flies which represented other living formsto similar doses. Many bugs initially survived after receiving 1,000 radsand 10,000 rads . However, only some flour beetles survived afterreceiving a dose of 100,000 rads. Fruit flies and flour beetles are foundto be tougher than cockroaches. For instance, on the second day afterreceiving 100,000 rads, all the cockroaches died; 40 per centof the fruit flies and 90 per cent of the flour beetles survived. Thesurvivors will be infertile.

“While cockroaches survived much more than the humans would,the other two test subjects did better than the cockroach,” the TVchannel declared. They concluded that they busted the myth since,more life forms than cockroaches survived!

The spectators’ reactions to the TV programme, revealed howdifferently the common man understands radiation related concepts.Is it safe to go into the room after cobalt irradiated the bugs? A viewerwanted to know. The questioner wrongly felt that irradiation withcobalt will leave the room radioactive!

One viewer objected to the use of cobalt radiation to irradiatethe bug. “Consideringthat the myth was “will cockroaches survivea nuclear blast” shouldn’t they have used uranium-238?” hequeried. “I believe that this is the substance used in modern daynuclear weapons,” he argued. (Obviously he did not understandthe difference between radiation from a nuclear weapon and thatfrom uranium-238).

It was equally wrong on the part of the TV channel to claim thatthey are exposing the insects to a nuclear blast when they actuallyexposed the bugs to gamma radiation from a cobalt source. Thesurvivability of cockroaches in a nuclear war has been a topic ofinterest for several years.

Based on the work of Hassett and Jenkins (Nucleonics, 1952),Professor John Moulder, Professor of Radiation Biology, MedicalCollege of Wisconsin, noted that about900-1,000 Gys are neededto kill a cockroach (one Gy= 100rads); more dose isrequired if the dose is delivered at a slower rate. The claim thatnot enough scientific data are available is not true.

Strong evidence

In 1957, Drs Wharton and Wharton found that 1,000 rad caninterfere with the fertility of cockroach. In 1963, Drs Ross andCochran found that a low dose of 6,400 rad would kill 93 per centof immature German cockroaches.

Inspite of such unimpeachable evidence on itsradiation-vulnerability, the myths about this unlovable creaturemay survive, not withstanding the fame and popularity of the‘Myth Busters.’